A fire truck continues to pour water on the No. 4 Crude Unit at the Chevron Refinery in Richmond, Calif. on Tuesday, Aug. 7, 2012, one day after an explosion and fire rocked the area and sent a giant plume of black smoke into the atmosphere.

Photo: Paul Chinn, The Chronicle

A fire truck continues to pour water on the No. 4 Crude Unit at the...

Unchecked corrosion, the suspected culprit in the August blaze that destroyed part of Chevron's Richmond refinery, was responsible for another fire at the plant last year that prompted workers to complain to regulators that the company was ignoring the problem, according to state inspection documents obtained by The Chronicle.

The state Division of Occupational Safety and Health inspector who investigated the smaller October 2011 fire - which occurred during a scheduled maintenance shutdown and was quickly extinguished - documented allegations from two workers that corrosion was attacking the refinery and that employees could be at risk.

"We're afraid something is going to fall through the cracks," one worker told Cal/OSHA safety inspector Carla Fritz, who was investigating the fire in furnace piping at the refinery's lube oil processing plant. His comments are documented in notes Fritz took during her two-day plant visit in November.

Equipment wear

"We're concerned about increased corrosion - we've increased temperatures and increased rates, and it takes a toll on the equipment," said the worker, who was identified in Fritz's notes as head operator of the lube oil plant - the most senior of a 20-member operator crew.

The Chronicle obtained Fritz's notes under the state Public Records Act. State officials redacted the names of Chevron employees she interviewed.

Company managers told Fritz that although the corrosion that led to last October's fire was unexpected, nothing they found after that was out of the ordinary.

Asked by The Chronicle whether the earlier corrosion-related fire should have prompted checks throughout its refinery, Chevron did not respond directly but said in a statement that it had taken "the appropriate actions to protect the safety of its employees and facilities."

August fire

Chevron said last month that corrosion caused by high-temperature, high-sulfur oil was the likely cause of a pipe rupture that led to a major fire in the crude-processing unit Aug. 6, which knocked part of the Richmond refinery offline and significantly reduced its capacity at least until the end of the year. More than 15,000 people downwind of the blaze went to hospitals, complaining of respiratory and other problems caused by the smoke.

The company has conceded it neglected to inspect the failed 5-foot section of line for corrosion when it conducted the scheduled maintenance shutdown in October and November 2011. Federal investigators from the U.S. Chemical Safety Board discovered after the fire that corrosion had eroded 80 percent of the carbon-steel pipe wall's thickness, well above the level at which Chevron's policies called for replacement.

California worker-safety regulators say they have expanded their investigation of the August fire beyond the crude-processing unit to probe how Chevron has been handling pipeline leaks elsewhere at the Richmond plant and at the company's refinery in El Segundo (Los Angeles County).

Federal investigators said they are examining whether the earlier Richmond fire, combined with the August blaze, signaled a pattern of problems at Chevron's refinery.

Worker's complaint

The issue of corrosion from higher-sulfur oil attacking carbon steel pipe came up during the probe of the first fire on Oct. 3, 2011.

Fritz's visit was prompted by a complaint that an unidentified refinery worker had filed with Cal/OSHA, saying there were "unsafe working conditions" in the lube oil plant because of severe corrosion. The worker cited the October fire as evidence. Fritz declined to be interviewed for this story, referring questions to agency public affairs officials.

Fritz's notes show that the Richmond refinery's maintenance manager and managers on the plant's safety team acknowledged that corrosion had caused the rupture of a carbon steel pipe and the ensuing fire. The maintenance manager told her, according to her notes, that the corrosion - which occurred at an elbow of the furnace's piping - was unexpected.

Same material

The elbow was installed in 1983 and linked two pieces of more corrosion-resistant pipe. It was made of the same pipeline material that failed in August and that Chevron now says is susceptible to sulfur-induced corrosion if it is low in silicon.

Fritz's report does not address the silicon issue. But Cal/OSHA said in a statement to The Chronicle that the pipe "was made of the wrong type of metal for the type of corrosive crude oil flowing through it, creating a risk of fire and breakdown."

One Chevron inspector told Fritz that he did not believe the 2011 fire "suggested a larger problem" with corrosion at the refinery.

The lube oil plant's operations assistant, another manager who oversees operations at the unit, told Fritz the corrosion that Chevron found elsewhere in the plant during the maintenance shutdown was "pretty routine."

But the lube oil unit's head operator - one of two workers who expressed concern about the corrosion - said higher-sulfur oil that Chevron was processing was wearing away pipes throughout the unit.

"Some of the engineers were surprised at the corrosion," he told Fritz, according to her notes. He also complained that safety checks during the October-November maintenance shutdown were being cut short.

"People are saying they're complete, and they're not," he said, according to her notes.

Workers 'ignored'

The head operator also worried that Chevron's shutdown coordinator was making last-minute decisions about whether to restart the lube oil unit or delay the process for further inspections or repairs.

"We're afraid something is going to fall through the cracks when you've got one person, who's being pressured to get the plant up," making critical safety decisions at the end of the process, the head operator said.

The shutdown coordinator, also interviewed by Fritz, said that although Chevron inspectors had caught most of the corrosion during the maintenance shutdown, they had missed corrosion in at least one spot, inside a distillation column. That corrosion was caught by outside contractors shortly before the unit was to have been given the go-ahead to restart.

Another worker, identified only as an operator, told Fritz he was concerned that management was not doing more inspections in light of the fact that "lots of corrosion" had been found.

"My primary concern is we (get) ignored. We operate these plants, we walk by this equipment every day," the worker said.

In the end, after reviewing Chevron documents about its corrosion inspection process, Fritz issued no violation notices and allowed the company to restart the lube oil unit on schedule.

Two months later, her notes show, she called a meeting with Chevron officials to convey the workers' concerns that they "get ignored." The refinery officials assured her that they would do more inspections for corrosion while the plant was in operation.

Cal/OSHA said in a statement that Fritz had not issued a violation notice to Chevron over the 2011 fire "because the problem alleged and potential hazard had been already identified and corrected."

It said Chevron had a larger obligation, though.

"Armed with knowledge of improper metals used in processing a corrosive product in one part of the refinery," Chevron "was responsible for investigating other metals used in processing corrosive products throughout the refinery to assure their safety," the agency said.

Chevron's response

In response to questions about corrosion and last October's fire, Chevron said it "took the appropriate actions to protect the safety of its employees and facilities" after the blaze. "We immediately responded, shut down the affected operations, evacuated all nonessential staff and successfully contained the incident."

Officials with the U.S. Chemical Safety Board said federal rules requiring refineries to routinely inspect equipment are designed to prevent the kind of fires that occurred at Chevron.

The board's managing director, Daniel Horowitz, said federal investigators are scrutinizing last October's fire for similarities to the larger Aug. 6 blaze.

"We are particularly interested in prior refinery incidents that involve running process equipment to the point of failure," Horowitz said, adding that other probes "almost invariably have revealed that major chemical process accidents are preceded by numerous smaller warning signs."